[Elecraft] K3 transmit/amplifier relay

[Scott Ellington]

It may NOT be a good idea to gate the KEY_OUT with the foot switch because of timing issues.  If you release the foot switch while transmitting, the amplifier relay, especially a fast QSK relay, could release before the K3 RF output decays, resulting in hot-switching of the relay.  KEY_OUT apparently does not have that problem, or there would be lots of fried relays out there, not to mention key clicks.  I suppose you could add a delay to the foot-switch release gating, if you really thought it was worth the trouble.

The only way to properly gate KEY_OUT to be inactive in PTT RX mode is to do it internally to the K3.  As I said earlier, that is clearly not practical.  It's not the way I would have done it, but it's a minor thing.  In any design, trade-offs have to be made.

73,

Scott  K9MA

****

On Fri, 11 Mar 2011 20:51:00 -0500
 Don Wilhelm <w3fpr at embarqmail.com> wrote:

.....

> 
> So that is why KEY OUT is activated when the key is operated.  If that 
> does not suit your station setup, and you operate with a footswitch for 
> PTT, then it is an easy matter to use a relay (which is activated with 
> your footswitch) and connect the NO contacts in series the K3 KEY OUT line.
>